WO2017125495A1

WO2017125495A1 - Process for preparing a catalyst composition from microalgae

Info

Publication number: WO2017125495A1
Application number: PCT/EP2017/051085
Authority: WO
Inventors: Jacques Biton; Brice-Loïc RENARD; Elise Salanouve
Original assignee: Stratoz
Priority date: 2016-01-19
Filing date: 2017-01-19
Publication date: 2017-07-27

Abstract

The present invention pertains to a process for preparing a catalyst composition comprising the successive steps of (i) loading a microalgae with one or more heavy metals and (ii) thermally and optionally chemically treating said microalgae so as to obtain said catalyst composition. This invention also pertains to the catalyst composition thus obtained and to its use for catalyzing organic synthesis reactions.

Description

PROCESS FOR PREPARING A CATALYST COMPOSITION FROM

MICROALGAE

The present invention pertains microalgae to a process for preparing a catalyst composition comprising the successive steps of (i) loading a microalgae with one or more transition metals and (ii) thermally and optionally chemically treating said microalgae so as to obtain said catalyst composition. This invention further pertains to the catalyst composition thus obtained and to its use for catalyzing organic synthesis reactions. BACKGROUND OF THE INVENTION

With the rapid industrial development of many countries, various wastes containing metal ions are directly and indirectly discharged into the environment, bringing about serious environmental pollution and threatening marine life.

Municipal and industrial sewage is generally treated today by processes including sedimentation, bacterial action and chlorination. The result of such processes is wastewater generally free from particulate organics but still high in nutrients. Moreover, the water may still be contaminated by heavy metals including transition metals. Heavy metals present in water may also originate from soils where they are naturally present and from where they migrate due to leaching or solubilization from ores. It has been known to remove metallic pollutants from waste waters utilizing plants which are able to hyperaccumulate metals in their roots. This process is called rhizofiltration. Another bioremediation technique involves the removal of metal pollutants by microalgae, either by bioadsorption on an algal dead biomass immobilized on a synthetic polymer matrix or on an inorganic support material (such as the beads marketed in the trade name Bio-Fix^® or the product marketed as AlgaSorb^®) or by bio-accumulation by a living biomass. However, to the inventors' knowledge, it has never been suggested that the microalgal biomass obtained could be upgraded to take advantage of the metals it contains, instead of being recycled or disposed of or used to produce organic compounds such as biofuels, organic fertilizers or lipids. On the contrary, attempts have been made to upgrade terrestrial plant materials that have adsorbed or bio-accumulated metals or metalloids, so as to prepare catalyst compositions therefrom (WO 2011/064487). Specifically, the plant is first calcined to partially destroy the organic matter, then stirred in an acid, in particular hydrochloric acid or sulphuric acid, in order to destructure the plant and to obtain a mixture containing the calcined and destructured plant and at least one metal catalyst, the metal of which is chosen in particular from Zn, Ni, Mn or Cu. Then the mixture is concentrated, filtered, and the pH of the filtrate is adjusted as a function of the metal. It has also been suggested by H. L. Parker et al in PLOS One, Vol. 9, Issue 1 (January 2014) that a specific plant, namely wild-type Arabidopsis, may be used to accumulate palladium from contaminated soils to provide metal nanoparticles useful as a catalyst for Suzuki- Miyaura coupling reactions. This approach has several practical limitations. First, the catalyst compositions obtained have a complex structure which, inter alia, include catalyst poisons in addition to polymetal complexes, whereas catalysts with a simpler structure would be more useful for a number of organic reactions and would avoid the need for purification steps. Moreover, terrestrial plants need to be grown directly on polluted soils and their ability to accumulate metals will greatly vary depending on the nature of the soil and other environmental factors, which detrimentally affects the reproducibility of this process. Furthermore, this process can hardly be used for industrialized production of catalysts under economically acceptable conditions because, inter alia, the plants must be harvested and shipped to another location where they have to be treated in order to recover the metals contained therein.

SUMMARY

In view of the foregoing, there remains the need for a reproducible process for preparing a catalyst composition from renewable material, under economically favorable conditions.

This need can be satisfied by using a microalgal biomass for preparing such a catalyst composition. This invention is thus directed to microalgaea process for preparing a catalyst composition comprising the successive steps of (i) loading a microalgae with one or more transition metals and (ii) thermally and optionally chemically treating said microalgae so as to obtain said catalyst composition.

This invention is also directed to a catalyst composition obtainable according to the above process and to its use for catalyzing organic synthesis reactions including isomerization, hydrolysis, alcohol halogenation, epimerization, esterification, transesterification, aldolisation, alkylation, electrophilic substitution, heterocycles synthesis, multicomponent reactions, acylation, condensation, polymerization, coupling reactions, cyclization, metathesis, cycloaddition, carbonyl olefination, C-glycosidation, oxidation, epoxidation, reduction and hydrogenation. In addition to being easier to conduct on an industrial scale than processes using metal- accumulating plants, the process according to this invention allows, in some embodiments, the production of metallic particles in a reduced form which is more suitable for catalytic applications. Moreover, microalgae generate an amount of biomass to be treated that is significantly lower than plant biomass and that includes a higher content in the metal to recover. Furthermore, the present inventors have shown that the catalytic load required for conducting organic reactions is lower in the case of microalgae-derived metals than when using plant-derived metals (namely 0.001 to 0.1% in this invention, compared to 12% in the above publication by H.L. Parker et al.). DETAILED DESCRIPTION

Definitions

The following definitions apply in the context of this description.

"Microalgae", refers to microscopic algae which encompass both prokaryotic micro- organisms (cyanobacteria) and eukaryotic microorganisms. This term is preferably used to refer to living microalgae. "Effluent" refers to any liquid fraction which is discarded after a treatment has been performed in order to separate it from a valuable fraction.

"Transition metals" designates chemical elements from block d of the periodic table corresponding to groups 3 to 12 and periods 4 to 7 of the periodic table, except Lu (a lanthanide) and Lr (an actinide) and also the said "inner transition metals" which correspond to lanthanides and actinides (i.e. block f of the periodic table). These metals are present in a water medium in the form of ions or metallic particles and that should be removed from the medium, due to toxicological reasons, before the medium is disposed of in the environment or used for consumption. Examples of transition metals are cobalt, cadmium, chromium, copper, iron, manganese, molybdene, silver, gold, nickel, zinc, palladium, platinum, rhodium, ruthenium and their cations.

"Adsorption" means, in the context of this invention, rapid and reversible binding of ions and metallic particles (for instance zero-valence state metallic particles) from aqueous solutions onto functional groups that are present on the surface of biomass, either by ion exchange, complexation or electrostatic interactions. This process is independent from cellular metabolism.

"Bio-accumulation" refers to intra-cellular accumulation through a microalgal cell membrane, by endocytosis or by active transport. The taking up of metal is thus metabolically controlled and occurs when extracellular concentration of metals (ions or metallic particles) is higher than that of intracellular.

"Catalyst composition" means a composition comprising at least one metal, preferably in the form of a cation combined with a counter-ion or in the form of metallic particles (for instance zero-valence state metallic particles), which is suitable for catalyzing an organic synthesis reaction and which is able to be recovered in the same chemical form after the reaction and recycled to catalyze a further reaction.

The process according to this invention comprises a first step of loading a microalgae with one or more transition metals. Preferably, this step comprises cultivating microalgae in a liquid aqueous medium comprising one or more transition metals, and allowing said microalgae to adsorb and/or bio-accumulate at least one of said metals. Transition metals that are preferably used in this invention include, and preferably consist of, manganese, zinc, gold, copper and/or palladium. The liquid aqueous medium comprising one or more metals may be a municipal, industrial, mine or stone quarries effluents, for instance, or contaminated natural water such as ponds, lakes, rivers and groundwater.

The microalgae that may be used in this invention can be selected from chlorophyceae, such as those of the genus Chlamydomonas, Ankistrodesmus, Coccomyxa, Closterium, Coelastrum, Dictyosphaerium, Dunaliella, Haematococcus, Tetraselmis, Scenedesmus, Selenastrum, Pediastrum and Starastrum and from the Scenedesmaceae such as those of the genus Coelastrum; cyanobacteria such as those of the genus Chlorella, Parachlorella and Oscillatoria; cyanophycea such as those of the genus Plectonema, Arthrospira and Spirulina; chrysophyceae, such as those of the genus Mallomonas, Dinobryon, Peridinium and Uroglena; Coccolithophyceae, such as those of the genus Emiliania, Gephyrocapsa, Ochrosphaera and Pleurochrysis; Diatoms such as those of the genus Phaeodactylum, Thalassiosira, Melosira, Asterionella, Cyclotella, Cymatopleura, Somphonema, Fragilaria, Stephanodiscus, Navicula and Skeletonema; Euglenophyceae such as those of the genus Phacus, Trachelomonas and Ceratinium; and Rhodophyceae such as those of the genus Cyanidioschyzon, Cyanidium, Galdieria, Porphyridum and Rhodella. According a preferred embodiment of this invention, the microalgae belong to the genus Scenedesmus, Chlorella, Parachlorella or Chlamydomonas. For instance, the following microalgae may be used for bio-accumulating the following transition metals:

Microalgae Metal

Chlamydomonas reinhardtii Pd

Scenedesmus acutus Mn

Scenedesmus obliquus

Chlorella sorokiniana

Chlorella vulgaris

Chlorella vulgaris Zn

Scenedesmus obliquus

Parachlorella kessleri The microalgae may be grown in heterotrophic conditions, such as in fermenters, or in autotrophic conditions, for instance in photobioreactors. Photobioreactors may take the form of straight tubes arranged flat on the ground or in long vertical rows or of tubes that are spirally wound around a central support or a similar helical structure. The tubes can be of glass or synthetic polymer such as PVC. The fermenter or photobioreactor may be provided with means to control temperature, pH, air flow, dissolved oxygen, stirring and/or light conditions. According to a preferred embodiment of this invention, the microalgae are grown in autotrophic conditions.

The skilled person will be able to adjust the culture conditions depending on the microalgae used and on the metal(s) to recover. The culture medium may for instance be supplemented with any suitable nutrient(s) such as phosphorus, nitrogen, magnesium, calcium, potassium and/or sulfur sources. As nitrogen sources, mention can be made of urea, ammonium sulfate, sodium glutamate, proteins, or any appropriate mixture thereof, for instance. Glucose, fructose, sucrose, carbon dioxide, ethanol or any other appropriate compound may be used as a carbon source. Moreover, phosphate salts are generally used as a source of phosphorus and calcium chloride may be used as a source of calcium. The culture medium may further comprise at least one buffer and/or vitamins and/or chelating agents and/or trace metals and/or pH adjusting agents. The microalgae may for instance be grown at a pH of from 2 to 8. In addition, the algal biomass may be deprived of some nutrients during growth, so as trigger stress conditions which may be beneficial for the accumulation or adsorption of metals. The algae may further be grown in aerobic or anaerobic conditions. During growth the medium may or may not be circulated using a water wheel, paddle, a pump, or by pumping air or gas through the medium. Finally, once the desired amount of growth has been achieved, the biomass is harvested. The harvested biomass has adsorbed and/or bio-accumulated one or more of the metals present in the liquid aqueous medium. The biomass may then be concentrated by microfiltration and/or centrifugation. Alternatively or in addition thereto, it may be washed one or more times with an aqueous solution. In order to recover the metals, the biomass is then thermally treated.

In this respect, different thermal treatments may be implemented according to this invention. If desired, they may be followed by a chemical treatment intended to convert the thermally treated biomass into a desired catalyst composition.

According to a first embodiment, said thermal treatment comprises calcining said biomass at a temperature of from 400 to 600°C, such as at 500°C + 50°C, so as to obtain metal salts. This step may be performed in a muffle furnace, preferably for about 1 to lOh, for instance for 5 to lOh. This process optionally comprises a further step of chemically treating said calcined biomass so as to convert said metal salts into metal hydroxides, for instance by reacting said metal salts with an inorganic or organic acid, such as hydrochloric acid, optionally filtering the calcined biomass and concentrating said filtrate, and then preferably adding a strong base, such as sodium hydroxide or ammonium hydroxide at a pH of at least 12, for instance. The addition of this base allows the precipitation of metal hydroxides.

According to a second embodiment, the thermal treatment comprises incinerating said biomass at a temperature of 1000°C + 100°C, so as to obtain metal oxides, and said process optionally comprises a further step of converting said metal oxides into metal salts, for instance by reacting said metal oxides with an inorganic or organic acid, such as hydrochloric or sulphuric acid, and then possibly into metal hydroxides by reacting said salts with a strong base, such as sodium hydroxide at a pH of at least 13, for instance. While the above embodiments are conducted under air, i.e. under an oxidizing atmosphere, the thermal treatment may alternatively be performed under inert or reducing atmosphere, so as to prevent the oxidation of the transition metal which thus remains in the oxidation state in which it has bio-accumulated. For instance, it has been shown that palladium present in the form of Pd(II) in an effluent bioaccumulated as Pd(0) in microalgae. It has further been shown that this embodiment led to smaller catalyst particles which may be advantageous from the viewpoint of catalyst efficiency. Moreover, coal that will be formed may be used as a carrier for performing heterogeneous catalysis. The temperature at which this thermal treatment will be conducted and its duration depends on the metal used and can be easily adjusted by the skilled person so as to minimize the aggregation of metal particles and its loss of efficacy and/or to obtain the desired carrier. This thermal treatment may for instance be conducted for 1 to 10 hours, usually for 2 to 5 hours, at a temperature comprised between 200 and 1000°C, preferably between 400 and 600°C. In this embodiment of the invention, it is normally not required to carry out any chemical treatment, such as an acidic treatment, of the thermally-treated biomass.

The process of this invention may further comprise a step of drying and optionally grinding said biomass before said thermal treatment. Alternatively or in addition, it may comprise a step of drying the metal salts, hydroxides or particles formed as described above.

It should be noted that carbon dioxide released during the above calcination and incineration steps may be recycled as a nutrient into the microalgae culture.

The catalyst composition obtained according to this invention generally comprises from 0.1 to 30 wt.% of the transition metal except Fe, from 0 to 2 wt.% of Fe, from 0 to 2 wt.% of Al, from 0 to 30 wt.% of Ca, from 0 to 30 wt.% of K, from 0 to 30 wt.% of Mg, from 0 to 20 wt.% of Na and from 0 to 1 wt.% of other metals, relative to the dry matter content of the catalyst composition. The above "other metals" depend from the effluents treated and from the specific culture medium used to grow the microalgae.

This composition may be used as such or may be blended with an inert inorganic carrier such as alumina, silica, baryte, hydrotalcite, metal oxides such as ferrite, silicates such as montmorillonite, sepiolite or aluminosilicates, so as to obtain a supported catalyst. This blend may preferably be made by mixing the catalyst composition described above with the inert carrier in an aqueous medium, filtering the solid matter and drying the same. Alternatively, the catalyst composition and the inert carrier may be blended by co-grinding. In still another embodiment, the inert carrier may be used to grow the microalgae thereon. Preferably, the catalyst composition is used as such as a catalyst. This catalyst may be used to catalyze various organic synthesis reactions including isomerization, hydrolysis, alcohol halogenation, epimerization, esterification, transesterification, aldolisation, alkylation, electrophilic substitution, heterocycles synthesis, multicomponent reactions, acylation, condensation, polymerization, coupling reactions, cyclization, cycloaddition, metathesis, carbonyl olefination, C-glycosidation, oxidation, epoxidation, reduction and hydrogenation.

EXAMPLES

The following examples are provided for illustration purposes only and do not intend to narrow the scope of this invention which is defined by the attached claims.

Example 1: Preparation of a Zn catalyst from microalgae

Preparation of the microalgal culture

A microalgae stock solution was prepared from commercial sources in order to inoculate the effluent used for metal accumulation.

BG11 growth medium was used, according to its composition given in Table 1.

Table 1. Composition of BG11 growth medium 100 mL of BG11 medium were adjusted to pH 8 with tetramethylammonium hydroxide, then autoclaved (120 °C, 15 min), before being inoculated to 2.5 x 10⁵ cells.mL^"1 of Scenedesmus obliquus. Cultures were incubated at 23 °C with rotary incubation (150 cycles.min^"1), under a photon fluence incident on the surface of 12 μΕ.ιη ².s^_1, provided by white fluorescent light tubes. The cultures were aerated with 2% CO2 in air at a flow rate of approximately 150 mL.min^"1. After 20 days of incubation the cultures reached their exponential phase of growth and could be inoculated to the effluent. Metal accumulation

A 10 L photoreactor containing a Zn effluent (10 ppm Zn) was inoculated with the microalgae stock solution, then incubated for the necessary time until a minimal cell density of 5 x 10⁷ cells.mL^"1 was reached. The cultures were maintained in the same conditions than previously (23 °C, 150 rpm stirring, photon fluence incident on the surface of 12 μΕ.ιη^"2^^"1, provided by white fluorescent light tubes, the cultures were aerated with 2% CO2 in air at a flow rate of approximately 150 mL.min^"1). Once the cell density of 5 x 10⁷ cells.mL^"1 was obtained, the metal accumulation was continued for 8 h, reaching a maximum of 10 nmol/10⁷ cells. The microalgae were harvested by centrifugation (1000 x g, 5 min). The cells were collected and subjected to a drying thermal treatment in an oven (110 °C, 6 h) until constant weight.

Preparation of Zn catalyst after accumulation The dry microalgal matter resulting from the previous step was grinded into a powder, spread on plates (20 cm x 20 cm) into thin layers then subjected to a thermal treatment in a muffle furnace, open to air, at 500 °C for 5 h.

After this thermal treatment, the resulting powder was collected, and then poured into a 250 mL flask. A volume of hydrochloric acid (6 M) corresponding to 10 mL of hydrochloric acid by gram of powder was introduced. The mixture was stirred at 400 rpm at 60 °C for 6 h. The dark resulting solution was filtered and then the resulting filtrate was concentrated under reduced pressure, to afford a solid which was grinded into a powder. This resulting Zn catalyst was kept in a desiccator under reduced pressure.

Example 2: Preparation of a Mn catalyst from microalgae Preparation of the microalgal culture

A microalgal stock solution was prepared from commercial sources in order to inoculate the effluent used for metal accumulation.

BG11 growth medium was used, according to its composition given in Table 1.

100 mL of BG11 medium were adjusted to pH 8 with tetramethylammonium hydroxide, then autoclaved (120 °C, 15 min), before being inoculated to 2.5 x 10⁵ cells.mL^"1 of Scenedesmus obliquus. Cultures were incubated at 23 °C with rotary incubaction (150 cycles.min^"1), under a photon fluence incident on the surface of 12 μΕ.ιη ².s^_1, provided by white fluorescent light tubes. The cultures were aerated with 2% CO2 in air at a flow rate of approximately 150 mL.min^"1. After 20 days of incubation the cultures reached their exponential phase of growth and could be inoculated to the effluent.

Metal accumulation A 10 L photoreactor containing a Mn effluent (10 ppm Mn) was inoculated with the microalgae stock solution, then incubated for the necessary time until a minimal cell density of 5 x 10⁷ cells.mL^"1 was reached. The cultures were maintained in the same conditions than previously (23 °C, 150 rpm stirring, photon fluence incident on the surface of 12 μΕ.ιη^"2^^"1, provided by white fluorescent light tubes, the cultures were aerated with 2% CO2 in air at a flow rate of approximately 150 mL.min^"1). Once the cell density of 5 x 10⁷ cells.mL^"1 was obtained, the metal accumulation was continued for 8 h, reaching a maximum of 5 nmol/10⁷ cells. The microalgae were harvested by centrifugation (1000 x g, 5 min). The cells were collected and subjected to a drying thermal treatment in an oven (110 °C, 6 h) until constant weight. Preparation of Mn catalyst after accumulation

The dry microalgal matter resulting from the previous step was grinded into a powder, spread on plates (20 cm x 20 cm) into thin layers then subjected to a thermal treatment in a muffle furnace, open to air, at 500 °C for 5 h.

After this thermal treatment, the resulting powder was collected, and then poured into a 250 mL flask. A volume of hydrochloric acid (6 M) corresponding to 10 mL of hydrochloric acid by gram of powder was introduced. The mixture was stirred at 400 rpm at 60 °C for 6 h. The dark resulting solution was filtered and then the resulting filtrate was concentrated under reduced pressure, to afford a solid which was grinded into a powder. This resulting Mn catalyst was kept in a desiccator under reduced pressure.

Example 3: Preparation of a Pd catalyst from microalgae Preparation of the microalgal culture

BG11 growth medium was used, according to its composition given in Table 1.

100 mL of BG11 medium were adjusted to pH 8 with tetramethylammonium hydroxide, then autoclaved (120 °C, 15 min), before being inoculated to 2.5 x 10⁵ cells.mL ¹ of Scenedesmus obliquus. Cultures were incubated at 23°C with rotary incubaction (150 cycles.min^"1), under a photon fluence incident on the surface of 12 μΕ.ιη ².s^_1, provided by white fluorescent light tubes. The cultures were aerated with 2% CO2 in air at a flow rate of approximately 150 mL.min^"1. After 20 days of incubation the cultures reached their exponential phase of growth and could be inoculated to the effluent.

Metal accumulation A 10 L photoreactor containing a Pd effluent (10 ppm Pd) was inoculated with the microalgae stock solution, then incubated for the necessary time until a minimal cell density of 5 x 10⁷ cells.mL^"1 was reached. The cultures were maintained in the same conditions than previously (23 °C, 150 rpm stirring, photon fluence incident on the surface of 12 μΕ.ηι ²^ ¹, provided by white fluorescent light tubes, the cultures were aerated with 2% CO2 in air at a flow rate of approximately 150 mL.min^"1). Once the cell density of 5 x 10⁷ cells. mL^"1 was obtained, the metal accumulation was continued for 8 h, reaching a maximum of 10 nmol/10⁷ cells. The microalgae were harvested by centrifugation (1000 x g, 5 min). The cells were collected and subjected to a drying thermal treatment in an oven (110 °C, 6 h) until constant weight.

Preparation of two different Pd catalysts after accumulation

- The dry microalgal matter resulting from the previous step was grinded into a powder, spread on plates (20 cm x 20 cm) into thin layers then subjected to a thermal treatment in a muffle furnace, open to air, at 500 °C for 2 h.

After this thermal treatment, the resulting powder was collected, and then poured into a 250 mL flask. A volume of hydrochloric acid (6 M) corresponding to 10 mL of hydrochloric acid by gram of powder was introduced. The mixture was stirred at 400 rpm at 60 °C for 6 h. The dark resulting solution was filtered and then the resulting filtrate was concentrated under reduced pressure, to afford a solid which was grinded into a powder. This resulting Pd catalyst was kept in a desiccator under reduced pressure.

- The dry microalgal matter resulting from the previous step was grinded into a powder, spread on plates (20 cm x 20 cm) into thin layers then subjected to a thermal treatment in a muffle furnace, closed and under inert or reducing atmosphere, at 400 °C for 5 h.

After this thermal treatment, the resulting powder was collected, grinded and mixed. This resulting Pd catalyst was kept in a desiccator under reduced pressure.

Example 4: Friedel-Crafts benzylation of p-xylene with Zn catalyst

Liquid phase benzylation of /^-xylene with benzyl chloride was carried out in a three necked round-bottomed flask (25 mL) equipped with a reflux condenser and magnetic stirring. 3 mL (24 mmol) of /^-xylene were added to 780 mg of Zn catalyst as prepared in Example 1 (0.077 mmol of Zn, 10 mol ) placed in the flask and the mixture was heated to 80 °C. The mixture was maintained for 10 min at 80 °C, and then 0.69 mL (6 mmol) of benzyl chloride was added dropwise. The mixture was heated for 3 h then cooled to room temperature. The catalyst was filtered, rinsed with toluene (3 x 20 mL) then dried in oven (110 °C) until the next run. The mixture was distilled under reduced pressure, affording l,4-dimethyl-2- (phenylmethyl) -benzene in 92 % yield.

Example 5: Synthesis of dihydropyrimidinone with Mn catalyst

The reaction was conducted in a three necked round-bottomed flask (25 mL) equipped with a reflux condenser and magnetic stirring. A solution of ethyl acetoacetate (520 mg, 4 mmol), benzaldehyde (424 mg, 4 mmol), urea (312 mg, 5.2 mmol) and 364 mg of Mn catalyst as prepared in Example 2 (0.2 mmol of Mn, 5 mol%) in 95% ethanol (10 mL) was heated to 80 °C for 10 h. The mixture was allowed to cool slowly to room temperature. On cooling, the product spontaneously crystallized from the solution. The solid was filtered, washed with cold ethanol (0 °C, 3 x 10 mL) then recrystallized in ethanol, affording 5-ethoxycarbonyl-6- methyl-4-phenyl-3,4-dihydropyrimidin-2(lH)-one in 85 % yield.

Example 6: Suzuki-Miyaura cross-coupling reaction of 4-bromoanisole and phenylboronic acid with Pd catalyst

In a round-bottom flask equipped with a glass stopper and a stirring bar were introduced phenylboronic acid (1.2 equiv., 1.2 mmol, 156 mg), potassium phosphate tribasic (3 equiv., 1.2 mmol, 681 mg) and 1.5 mg of Pd catalyst as prepared according to Example 3 (1.1 μιηοΐ of Pd, 0.1 mol%). N-Methyl-2-pyrrolidone (1.5 mL) and Η20 (0.5 mL) were then added. To the resulting solution was added the 4-bromoanisole (1 equiv., 1.07 mmol, 134 μί). The reaction mixture was stirred at 100 °C for 1 h. After cooling to room temperature, an aliquot of the reaction was taken and analyzed by GC-MS with the use of mesitylene as internal standard. The desired product, 4-methoxybiphenyl, was obtained in 96% yield. Similar experiments were performed with commercially available palladium, specifically 0.1 mol% of Pd and 0.01 mol% of Pd: the desired product was obtained with a yield of 90% (in 20 min) and 81% (in lh), respectively.

Claims

1. Process for preparing a catalyst composition comprising the successive steps of (i) loading a microalgae with one or more transition metals and (ii) thermally and optionally chemically treating said microalgae so as to obtain said catalyst composition.

2. The process of claim 1, wherein step (i) comprises contacting said microalgae with a liquid aqueous medium comprising one or more transition metals, and allowing said microalgae to adsorb and/or bio-accumulate at least one of said metals.

3. Process according to Claim 1 or 2, characterized in that said thermal treatment comprises calcining said biomass under an oxidizing atmosphere, at a temperature of from 400 to 600°C, so as to obtain metal salts, and said process optionally comprises a further step of chemically treating said calcined biomass so as to convert said metal salts into metal hydroxides, for instance by reacting said metal salts with an inorganic or organic acid and then preferably with a strong base.

4. Process according to Claim 1 or 2, characterized in that said thermal treatment comprises incinerating said biomass under an oxidizing atmosphere, at a temperature of 1000°C + 100°C, so as to obtain metal oxides, and said process optionally comprises a further step of converting said metal oxides into metal salts and possibly further into metal hydroxides.

5. Process according to Claim 1 or 2, characterized in that said thermal treatment is performed under inert or reducing atmosphere at a temperature comprised between 200 and 1000°C, for instance between 400 and 600°C.

6. Process according to any of Claims 1 to 5, characterized in that it further comprises a step of drying and optionally grinding said biomass before said thermal treatment.

7. Process according to any one of claims 1 to 6, characterized in that said transition metals include manganese, zinc, gold, copper and/or palladium.

8. Process according to any one of claims 1 to 7, characterized in that said microalgae are selected from chlorophyceae, such as those of the genus Chlamydomonas, Ankistrodesmus, Coccomyxa, Closterium, Coelastrum, Dictyosphaerium, Dunaliella, Haematococcus, Tetraselmis, Scenedesmus, Selenastrum, Pediastrum and Starastrum and from the Scenedesmaceae such as those of the genus Coelastrum; cyanobacteria such as those of the genus Chlorella, Parachlorella and Oscillatoria; cyanophycea such as those of the genus Plectonema, Arthrospira and Spirulina; chrysophyceae, such as those of the genus Mallomonas, Dinobryon, Peridinium and Uroglena; Coccolithophyceae, such as those of the genus Emiliania, Gephyrocapsa, Ochrosphaera and Pleurochrysis; Diatoms such as those of the genus Phaeodactylum, Thalassiosira, Melosira, Asterionella, Cyclotella, Cymatopleura, Somphonema, Fragilaria, Stephanodiscus, Navicula and Skeletonema; Euglenophyceae such as those of the genus Phacus, Trachelomonas and Ceratinium; and Rhodophyceae such as those of the genus Cyanidioschyzon, Cyanidium, Galdieria, Porphyridum and Rhodella, preferably said microalgae are selected from those from the genus Scenedesmus, Chlorella, Parachlorella or Chlamydomonas.

9. A catalyst composition obtainable according to the process as defined in any one of claims l to 8.

10. Use of the catalyst composition according to claim 9 for catalyzing organic synthesis reactions including isomerization, hydrolysis, alcohol halogenation, epimerization, esterification, transesterification, aldolisation, alkylation, electrophilic substitution, heterocycles synthesis, multicomponent reactions, acylation, condensation, polymerization, coupling reactions, cyclization, cycloaddition, carbonyl olefination, C-glycosidation, oxidation, epoxidation, reduction and hydrogenation.